Carrier localization and magnetoresistance in DNA-functionalized carbon nanotubes

Abstract

Helical functionalization of carbon nanotubes using DNA strands can polarize carrier spins through chirality induced spin selectivity (or CISS) effect. Detection of this effect using transport experiments unravels an underlying magnetoresistance effect, origin of which is not well understood. In the present study, we investigate this effect, a fundamental understanding of which is crucial for the potential use of this system in spintronic devices. The conduction mechanism has been found to be in the strongly localized regime due to DNA functionalization, with the observed magnetoresistance originating from the interference effects between the forward and backward hopping paths. CISS-induced spin polarization has been estimated to increase the carrier localization length by an order of magnitude in the low temperature range and it affects the magnetoresistance effect in a non-trivial way that is not observed in conventional systems.

Chirality-Induced Spin Selectivity in Heterochiral Short-Peptide–Carbon-Nanotube Hybrid Networks: Role of Supramolecular Chirality

“…48,49 A background negative MR is observed, which is a common occurrence in CNT networks. 41,42,50 This negative MR can arise from various sources, but in the present case, as discussed previously, 50 its origin is due to an interference effect between the forward and backward hopping paths. Most importantly, a MR asymmetry has been seen, i.e.…”

“…Magnetic field, and hence Ni magnetization, is perpendicular to the sample plane (θ = 90°) and therefore to all the current paths. Such a configuration allows us to eliminate any contribution from electromagnetochiral anisotropy effects that arise due to nonzero B · I terms. , A background negative MR is observed, which is a common occurrence in CNT networks. ,, This negative MR can arise from various sources, but in the present case, as discussed previously, its origin is due to an interference effect between the forward and backward hopping paths. Most importantly, a MR asymmetry has been seen, i.e.…”

Molecular Functionalization and Emergence of Long-Range Spin-Dependent Phenomena in Two-Dimensional Carbon Nanotube Networks

“…The direction of the magnetic field is perpendicular to the sample plane (θ = 90°); i.e., Ni magnetization is out-of-plane. A background negative MR is observed, which is a common occurrence in CNT networks 22,28,35,36,50 and originates from the magnetic field dependence of hopping conductivities in these samples. 28,35,36,56,57 Most importantly, we observe a non-zero Δ (= R(−12 kG) − R(+12 kG)/min [R(±12 kG)]) for each functionalization.…”

“…A background negative MR is observed, which is a common occurrence in CNT networks 22,28,35,36,50 and originates from the magnetic field dependence of hopping conductivities in these samples. 28,35,36,56,57 Most importantly, we observe a non-zero Δ (= R(−12 kG) − R(+12 kG)/min [R(±12 kG)]) for each functionalization. For the L samples Δ is negative, whereas for the D samples Δ is positive.…”

“…While organic molecules offer virtually limitless chemical tunability, they behave as insulators in terms of their bulk (long-range) electronic properties, which inhibits their direct integration with mainstream electronics or emerging two-dimensional (2D) nanoelectronics. , This can potentially be remedied by CNT-based CISS systems, which are more conductive than their organic molecular counterparts, and could provide a useful platform for practical spintronics devices. Initial studies have reported the CISS effect in one or few CNTs which are functionalized with helical single-stranded DNA. − Whether this effect persists in a 2D nanotube network functionalized with arbitrary chiral molecules remains unknown. The ability to induce spin polarization in a 2D CNT network would allow imparting spintronic functionalities to myriads of devices developed on this platform over the past few decades …”